In a development that robs the Jets on both defense and special teams, Jim Leonhard suffered what was believed to be a season-ending injury yesterday.

Leonhard, the valuable safety and sure-handed punt returner, injured his right knee in the Jets’ 37-10 romp over the Chiefs at MetLife Stadium. A source said the team believes Leonhard tore a knee ligament, saying, “It doesn’t look good.”

A torn knee ligament would mark the second straight season in which Leonhard’s year ended early due to injury. He broke the same leg last year and missed the regular season’s final five games, plus the playoffs.

“We did hear on the sideline that he may be out for the season,” cornerback Darrell Revis said. “Jim’s out again. You’ve just got to approach it like we did last year.”

Indeed, last season the Jets lost three of their first four when Leonhard initially went down, but they then won three in a row en route to the AFC title game in Pittsburgh. Brodney Pool and Eric Smith manned the safety positions, and both Pool and Smith will be the safeties the Jets rely on for the remainder of this season as well.

“We’ve got guys who’ve played a lot. It’s definitely a situation we’ve been in before,” linebacker Calvin Pace said. “It’s going to be tough. Somebody has got to go and study up and get ready to go. We’ve just got to keep moving.”

Leonhard has 48 tackles and one interception this season, and his lone pick sparked his injury. With 11:13 to play in the first half yesterday, Leonhard picked off a Tyler Palko pass at the Chiefs’ 38-yard-line. But Leonhard went down after the interception, and he had to be helped off the field.

What’s the value of the 29-year-old Leonhard?

Revis called him “one of the quarterbacks back there,” and he’s regarded as the secondary’s leader. Not only that, but the Jets now have zero depth at safety. Pool and Smith may be capable starters, but if one gets hurt, the Jets are in trouble.